Christina Aguilera welcomes Gwen Stefani to 'The Voice'

(Yahoo!) - She ain't no Hollaback Girl, but she's apparently a new "Voice" coach. As rumored, Gwen Stefani will be joining the show's Season 7 panel, sitting in one of those big red chairs alongside her longtime friend and collaborator, Pharrell Williams.

Who confirmed this news? A source very close to the show: none other than on/off original "Voice" coach Christina Aguilera, who tweeted her congratulations to her temporary replacement late Monday evening. (NBC reps had not yet responded to Yahoo's request for comment at press time.)

Gwen will be filling in for Christina — who, by the time Season 7 starts taping in June, will be close to nine months pregnant — and for current Season 6 coach Shakira, who will be spending the summer touring to promote her new album. Christina is expected to return to the show for Season 8, which airs in spring 2015.